Interiorly supported filter pad



July 19,- 1938. H. M. 'GAARDER INTERIORLY SUPPORTED FILTER PAD Filed DeC. 13, 1937 We rf /ferefi harder? @wmf MZ@ @m1/Uffa..

Patented July 19, 1938 UNITED STATESI PATENT OFFICE Herbert M.

Gaarder, Chicago,

Ill., assignor to Wilson & Co., a corporation of Delaware Application December 13, 1937, Serial No. 179,561

2 Claims.

This invention relatesv to an improved air filter pad and more particularly to such a pad prepared of loosely aggregated fibrous material within which is imbedded an open-work metallic 5 screen as a support.

Air filters of the impingement type. which remove dirt, dust, pollen and bacteria from gases by impingement, as distinguished from a straining process, have hitherto been customarily prepared and marketed in metal or cardboard containers. These containers are normally of the size of the opening in which the filter is to be employed, and the filtering medium iits inside Such covers are l5 made as open as possible, but still decrease the filtering area about or more, because they cover three-fourths ofan inch to an inch at the' edges and cover both the face and back of the filter to a considerable degree.

20 In my co-pending application, Serial No. 102,577 iiled September 25, 1936, is described a filter pad in which as a preferred embodiment the loose fibrous material is held between two exterior screens. Such a iilter is preferred for general purposes, but for certain other purposes a cheaper iilter may be prepared by embedding the metallic screen within the filtering material. Such an embedded support is particularly valuable where the filter is to be employed in a passageway already provided with a screen against which the filter may rest.

By means of the present invention,'as well as the invention set forth in my application Serial No. 102,577, an oversized pad may be readily prepared with resilient filtering edges which compress against the sides of the lter frame and provide a dust-tight ltering seal on all sides.

The invention is illustrated in the drawing in which: Figure 1 is a face view of a filter partially 40 cut away; Figure 2 is a cross-section taken along the line 2 in Figure 1, and also including in section a portion of the filtering passage; and Figure 3 is a face view partially cut awayyof a modied structure.

As illustrated in the drawing, theiilter comprises a mass of fibrous material I0 in which is embedded an open mesh screen The iibrous material extends beyond the edges of the screen,v

preferably not more than one inch and not less than one-half inch. The ends of the wires may be left protruding as indicated at I2.

It is preferable to employ Ia screen having as large a mesh as two inches for normal sized lters. The wires are'of small size and may be welded at the joints if desired. A 14-gauge galsupport vanized iron-wire frame is satisfactory with the elements spaced approximately two inches apart.

As an example of the invention, an air filter was produced by filling a square mold 201/2" on edge and approximately 2" in thickness with ap- 5 The hair is preferably ho hair which may include minor proportions of uncurled hog hair, say. 7 to 25%.

It may also include up to 10% of long hair such as cattle hair, horse tail hair, or horse mane hair. 10 The uncurled hair may be either intermixed with curled hair, or may be evenly distributed on one face of the filter, for example, the air exit face. The hair should be iiuied in order to provide proper density ratios, which should ordinarily be 15 within the range of one-half-to one and one-half ounces of hair per cubic inches of pad, and preferably three-fourths to one and one-fourth ounce. A thin pad, of course, is preferably more dense than a thick one, and with shorter hair 20 the density ranges may be somewhat higher.

In preparing the pad approximately one half of the hair is dropped into the mold in iiuffed condition, the screen is then dipped in adhesive and laid on top of the hair and the remaining 25 hair placed upon it. The `use of the adhesive upon`the screen is of considerable value in preventing separation of the hair about the screen. A preferred adhesive is latex.

After the screen has thus been embedded, the 30 loosely formed pad is then treated exteriorly with an adhesive to bind the outer hairs firmly together and provide an outer shell. This is preferablydone by spraying the formed pad with the adhesive. v

With a lter pad 201/2" square, a satisfactory screen is one 191/2 square, measured from the points of the wires, or, say, 181/2" square from the cross wires. With screens of lighter mesh, however, slightly less wide borders are preferred and v4,9 the screen maywell have its cross wires extend within 1/2" from the edge of the pad. In such an event, however, the Wires should be clipped off at the last cross wire.

When placed in a passageway 20 square, the 45 screen compresses to the size of the opening, but owing to the resilience of the hair, the take-up is transmitted several inches into the interior of the pad, the portion of the pad so aiected is not appreciably denser and maintains its original 50 iiltering efficiency. This is illustrated in Fig. 2, where the pad is shown with its upper edge contacting a wall I4 of a passageway. The filter pad is also shown as resting against a screen 5 afiixed to the walls of the passage. 55

This application is a continuation-impart oi.' my co-pending application Serial No. 102,577 led September 25, 1936.

The foregoing detailed description has been vgiven for clearness of understanding only and no limitations should be shown in Fig 3. In a specic example of such a construed as broadly as permissible, in view of pad, the margin of the screen to the edge of the the prior art. pad is 1/" to 1" on all edges except the top where I claim:

it is 4" to 41/2, the whole pad again being ap- 1. An airlterpadadapted to fit an opening` in proximately 201/2" square. In this case the pad an air passagewa comprising a pad of loosely is always placed with the wider margin at the distributed interconnected resilient brous nltop. A tering material, a coarse mesh screen-support While the illter has been described as of hair, embedded in the pad and glued to adjacent bers other similar may be employed Likewise, narrow mesh screen port the pad in operating position.

may be employed, but cuts down the eillciency of 2; An air lter pad adapted to t an opening the pad by increasing its resistance In no event in an air passageway comprising a pad of loosely should the lter be of a smaller mesh than a. y," distributed resilient brous material, a coarse opening, although, of course, if very strong and mesh screen support centrally embedded in the pad and secured to iibers touching it, the screen being of substantially smaller area than the pad. use, one face of the screen is sprayed or coated HERBERT M. GAARDER. with oil. y 

